The Hansa existed for some centuries. Originally it was an organisation of merchants, but as their guilds were connected to the towns where they lived, it soon became an organisation for towns. The towns which were members of the Hansa were not the same the whole time.
Visby is nowadays a part of the municipality of Gotland (...). Stockholm and Calmar (Kalmar) are thought to have been members of the Hansa for short periods, because in some sources they are mentioned as Hanseatic towns, but it could also be because the Hansa had offices there.
Elias Granqvist, 28 Mar 2001

Norie and Hobbs 1848 shows under
"150: Hanse Towns" a red flag, upper half white but leaving a narrow border of red along the top and fly. The German editors comment, "The hanseatic colours white and red never appeared in a common flag like no. 150. It could only represent some smaller Dutch cities which used to belong to the Hansa". They are not saying there never was such a common flag, which leaves room for the story that ships of Hansa-members raised a red pennant when entering a member-town or a town where the Hansa had privileges.
Peter Hans van den Muijzenberg, 12 Nov 2001

The word "Hansa" is the shortened form of the Lower German expression der blanke Hans / de blank haans ("blowing Hans") meaning "withstand the wind".
Jens Pattke, 22 Dec 2001

H. Zimmern, The Hansa Towns, 1889, p. 46, says: "The origin of the name of Hansa is wrapped in some mystery. The word is found in Ulfila's Gothic translation of the Bible, as signifying a society, a union of men, particularly in the sense of combatants. He applies it to the band of men, who came to capture Jesus in the garden of Gethsemane. Later on Hansa occurs as a tax on commercial transactions, and also as the sum, a very low one, which the various cities paid as their entrance fee into the association. The league acquired its name after its first great war with Waldemar of Denmark and the peace of Stralsund (1370)."
I didn't encounter "der blanke Hans", but he may well be part of popular etymology.
Jarig Bakker, 22 Dec 2001

Hanging Flags 13th-14th Centuries

Znamierowski 1999 shows several interesting flags of the Port Cities of northern Europe. These are derived from gonfanons, originally red in color. The flags, in a banner form [i.e. hanging flags], were flown from the stern of the vessels, the mast carrying the gonfanon of the colours. The oldest of the series that Znamierowski 1999 shows dates from the mid-13th century, that of Hamburg. It was followed by the flags of Riga, Lübeck
and in the 14th century by Stralsund, Elbing, Danzig, Bremen and Rostock.
The final three that Znamierowski 1999 shows for Königsberg, Wismar and
Stettin in the 15th century.
Phil Nelson, 20 Feb 2000